This invention relates to a method of quickly and easily curing adhesive substances. More specifically, this invention relates to such a method wherein radiation heat energy is cyclically applied to the adhesive substance in a controlled manner to ensure rapid curing of the adhesive substance without heating any portion of the adhesive substance to an excessive temperature level.
Curable adhesive substances in general are well known in the art and are used widely in a large number of industrial applications. For example, in one common industrial application, such adhesive substances are used in the manufacture of so-called insulated windows and/or doors. In the manufacture of these products, two panes of glass or other suitable glazing material are separated in parallel from each other by appropriate peripheral spacers and are mounted within appropriate rigid frames for a window or door. However, prior to mounting in the frame, a bead of a suitable curable adhesive substance is interposed between the two panes to help secure them together and to hermetically seal from atmosphere the insulation space between the two panes. In this manner, the two panes are more easily handled for installation into their respective frame, and condensation of moisture between the panes upon fluctuations in climatic conditions is avoided. Conveniently, it is known to provide a desiccant material such as a molecular sieve within the space for adsorption of moisture and/or gaseous fumes from within the insulating space.
In the manufacture of insulated windows and doors, it is highly desirable to cure the adhesive substance as rapidly and as completely as possible to maximize the production rate of the units. That is, the two panes of any given window cannot be moved or handled for any production purpose until the sealing bead of the adhesive substance is substantially completely cured. One common method of curing the adhesive substance is to allow the two panes to stand untouched while the adhesive substance cures at ambient temperature. Clearly, however, this procedure consumes a relatively long period of time, such as on the order of about four hours, and is therefore inconsistent with maximization of production rate. Moreover, substantial storage facilities are required to provide the necessary space for storage of units during curing of the adhesive substance.
Since these adhesive substances typically comprise polymeric resin substances formed from a mixture of base and accelerator materials, one way to speed curing of the adhesive substance is to increase the relative proportion of the accelerator material. This can, however, cause the substance to cure before it can be satisfactorily applied to the glass panes. In addition, this alteration of the substance composition can adversely affect both the sealing and the bond strength of the substance when cured.
Various other attempts have been proposed in the prior art for increasing the cure rate of the adhesive substance and thereby correspondingly increase the overall unit production rate. One such proposal comprises the placement of the units within a hot air oven to substantially elevate the temperature of the adhesive substance for purposes of curing the adhesive substance. However, this technique exposes the entire unit including the sealed insulation space between the two panes to the elevated temperature. This tends to increase the pressure level of the air trapped between the panes to cause displacement of portions of the adhesive substance to break the hermetic seal, or alternately, tends to cause the two panes to bulge outwardly with respect to each other.
An alternate proposal comprises subjecting the assembled units to relatively elevated but lower temperature levels within a hot air oven or in close proximity with a radiation heating device. Such arrangements are effective to increase the temperature levels of the adhesive substance to correspondingly increase the rate of curing of the adhesive substance. However, the use of a lower temperature hot air oven provides only marginal improvements over the prior art method of exposing the panels to ambient air for prolonged time periods. The exposure of the adhesive substance to radiant heat energy renders the substance susceptible to blistering and degradation as a result of localized overheating unless the radiation heat energy is applied at a relatively low power level. However, the use of low power radiation heat energy does not provide the desired rapid cure of the adhesive substance.
It is therefore desirable to provide an improved method for curing adhesive substances used in industrial applications wherein the adhesive substance is rapidly cured at a maximized cure rate by controlled cyclic application of radiation heat energy without overheating of the adhesive substance and without substantial heating of the surrounding air or structural components.